The meninges (from the Greek meninx, meaning “membrane”) cover and protect the brain and spinal cord. The meninges have three layers: 1) the dura mater, 2) the arachnoid, and 3) the pia mater. The dura mater is the outermost layer covering the central nervous system. The arachnoid (from the Greek arachne, meaning “spider”) is a weblike network of collagen and elastic fibers. The innermost layer of the meninges is the pia mater. The pia mater is firmly attached to the neural tissue of the spinal cord and brain. Cerebrospinal fluid fills the space between the pia matter and the arachnoid membrane. Most of the blood vessels that supply blood to the central nervous system are in the pia mater.